Microcephaly is a condition where a baby is born with a small head or the head stops growing after birth. Microcephaly is neonatal malformation defined as a head size much smaller compared with other babies of the same age and sex. Microcephaly can occur as an isolated condition, or it can occur in combination with other major birth defects.
According to World Health Organization (WHO), microcephaly is a rare condition. One baby in several thousand is born with microcephaly.
Brazil has reported an unusual, sudden increase in babies born with microcephaly since May 2015. Brazilian Live Birth Information System (SINASC) reported the prevalence of microcephaly in Brazilian newborns as 5.5 cases/100,000 live births and 5.7 cases /100,000 live births in 2000 and 2010 respectively. Over the last three months of 2015, it went up to 99.7 per 100.000 live birthsa.
Recently a base line estimate of birth prevalence of microcephaly affected births (total number of babies including both live born and stillborn with microcephaly per 10 000 births) in India was determined after a systematic review and meta-analysis of several studies. The pooled birth prevalence of microcephaly was shown as 2.30 per 10 000 births among 97155 birthsb.
Babies born with micocephaly often have smaller brains which have not developed properly. Other symptoms like convulsions, physical and learning disabilities start to appear as child grows older.
There are no specific tests to determine microcephaly during fetal life, but ultrasound scans in the third trimester of pregnancy can be used to identify the problem. The most reliable method to diagnose the microcephaly in new born is to measure head circumference 24 hours after birth, compare the value with WHO growth standards and continue to monitor the rate of head growth in early infancy.
a. Soares de Araújo JS, et al. Microcephaly in northeast Brazil: a review of 16 208 births between 2012 and 2015 [Submitted]. Bull World Health Organ E-pub: 4 Feb 2016. doi: dx.doi.org/10.2471/BLT
b. Bhide P, Kar A. Birth prevalence of microcephaly in India. [Submitted]. Bull World Health Organ E-pub: 23 Feb 2016. doi: dx.doi.org/10.2471/BLT.
Babies with microcephaly can have different types of symptoms depending upon the severity of microcephaly. Some children with microcephaly will develop entirely normally. Many babies born with microcephaly may show no other symptoms at birth but go on to develop:
There are various factors which cause microcephaly in newborns, but often cause remains unknown. The most common causes include following:
During the pregnancy:
According to WHO early diagnosis of microcephaly can be done by fetal ultrasound. Ultrasounds should be done at the end of the second trimester, around 28 weeks, or in the third trimester of pregnancy.
In fetuses with head circumference two standard deviations below the mean for gestational age, microcephaly should be suspected.
After child birth:
Head circumference of newborn babies should be measured when newborn baby is at least 24 hours old and compared with WHO growth standards in relation to the gestational age, sex, weight and length of the baby.
The measurement value for microcephaly is usually less than two standard deviations (2SDs) below the average. Severe microcephaly is defined as a head circumference less than three standard deviations (3SDs) below the average for babies of the same age and sex. (This means the baby’s head is extremely small compared to babies of the same age and sex.)
Suspected cases should be reviewed by a pediatrician, brain imaging scans such as computed tomography scan (CT scan), Magnetic resonance imaging (MRI) can be done. Their head circumference should be measured at monthly intervals in early infancy and compared with growth standards.
Doctors should also test for known causes of microcephaly.
Complications of microcephaly are secondary conditions or disorders that are caused by microcephaly. Many of the problems associated with microcephaly are developmental delays, problems with vision, hearing, or speech; and epilepsy, trouble moving their arms and legs and problems with feeding because of difficulties sucking and swallowing. A smaller head at birth is also associated with mental retardation.
There are no specific preventive measures; however few known factors causing microcephaly during fetal life may be prevented as-
a. Pregnancy management in the context of Zika virus- apps.who.int/iris/bitstream/